This invention relates to ultra hard or hard composite materials, and to methods of making them.
Ultra hard composite materials, typically in the form of abrasive compacts, are used extensively in cutting, milling, grinding, drilling and other abrasive operations. They generally contain ultra hard abrasive particles dispersed in a second phase matrix. The matrix may be metallic or ceramic or a cermet. The ultra hard or hard abrasive particles may be diamond, cubic boron nitride (cBN), silicon carbide or silicon nitride and the like. These particles may be bonded to each other during the high pressure and high temperature compact manufacturing process generally used, forming a polycrystalline mass, or may be bonded via the matrix of second phase material(s) to form a polycrystalline mass. Such bodies are generally known as polycrystalline diamond (PCD), or polycrystalline cubic boron nitride (PCBN), where they contain diamond or cBN as the ultra hard particles, respectively.
PCT application WO2006/032984 discloses a method of manufacturing a polycrystalline abrasive element, which includes the steps of providing a plurality of ultra hard abrasive particles having vitreophilic surfaces, coating the ultra hard abrasive particles with a matrix precursor material, treating the coated ultra hard abrasive particles to render them suitable for sintering, preferably to convert the matrix precursor material to an oxide, nitride, carbide, oxynitride, oxycarbide, or carbonitride of the matrix precursor material, or an elemental form of the matrix precursor material, or combinations thereof, and consolidating and sintering the coated ultra hard abrasive particles at a pressure and temperature at which they are crystallographically or thermodynamically stable. In this way ultra hard polycrystalline composite materials are made having ultra hard particles homogeneously dispersed in fine, sub-micron and nano grained matrix materials.
The ultra hard abrasive elements typically comprise a mass of ultra hard particulate materials of any size or size distribution smaller than about several hundred microns, down to and including sub-micron and also nano-sizes (particles less than 0.1 microns i.e. 100 nm), which are well dispersed in a continuous matrix made of extremely fine grained oxide ceramics, non-oxide ceramics, cermets or combinations of these classes of materials.
EP 0 698 447 discloses another approach to the generation of ultra hard composite materials, whereby the matrix is generated by the pyrolysis of organometallic polymer precursors, such as pyrolysis of polymerized polysilazanes. This has particular utility for the generation of ultra hard composites derived from diamond and/or cBN where the ceramic matrices are selected from silicon carbide, silicon nitride, silicon carbonitride, silicon dioxide, boron carbide, aluminium nitride, tungsten carbide, titanium nitride, and titanium carbide.